Morphological changes indicative of brain hemisphere development and handedness in fixed brains and on CT/MRI images.

We measured the lengths of some parts of the right and left hemispheres (HEs) in 70 formalin-fixed brains and on 15 computed tomography/magnetic resonance imaging (CT/MRI) images (7 left-handed and 8 right-handed cases) to clarify the morphological changes indicating which HE developed earlier and handedness. In many cases of the fixed brains, 1) the distance from the frontal pole to the occipital pole was longer in the left HE than in the right HE, 2) the distance from the middle plane to the lateral-most portion of the HE was wider in the right HE than in the left HE, 3) the left occipital pole elongated more posteriorly and covered the right occipital pole, and 4) the volume of each HE was nearly the same. The results indicate that the left HE develops and grows slightly earlier in the larger semi-cranium (half of the cranium) than the right HE which develops later in the smaller semi-cranium. The whole brain was more spherical in the female cases than in the male cases. The morphological changes in both HEs for handedness were not evident on the CT/MRI images.

Role of primate cerebellar hemisphere in voluntary eye movement control revealed by lesion effects.

The anatomical connection between the frontal eye field and the cerebellar hemispheric lobule VII (H-VII) suggests a potential role of the hemisphere in voluntary eye movement control. To reveal the involvement of the hemisphere in smooth pursuit and saccade control, we made a unilateral lesion around H-VII and examined its effects in three Macaca fuscata that were trained to pursue visually a small target. To the step (3 degrees)-ramp (5-20 degrees/s) target motion, the monkeys usually showed an initial pursuit eye movement at a latency of 80-140 ms and a small catch-up saccade at 140-220 ms that was followed by a postsaccadic pursuit eye movement that roughly matched the ramp target velocity. After unilateral cerebellar hemispheric lesioning, the initial pursuit eye movements were impaired, and the velocities of the postsaccadic pursuit eye movements decreased. The onsets of 5 degrees visually guided saccades to the stationary target were delayed, and their amplitudes showed a tendency of increased trial-to-trial variability but never became hypo- or hypermetric. Similar tendencies were observed in the onsets and amplitudes of catch-up saccades. The adaptation of open-loop smooth pursuit velocity, tested by a step increase in target velocity for a brief period, was impaired. These lesion effects were recognized in all directions, particularly in the ipsiversive direction. A recovery was observed at 4 wk postlesion for some of these lesion effects. These results suggest that the cerebellar hemispheric region around lobule VII is involved in the control of smooth pursuit and saccadic eye movements.

Role of primate cerebellar lobulus petrosus of paraflocculus in smooth pursuit eye movement control revealed by chemical lesion.

The primate lobulus petrosus (LP) of the cerebellar paraflocculus receives inputs from visual system-related pontine nuclei, and projects to eye movement-related cerebellar nuclei. To reveal a potential involvement of LP in oculomotor control, we lesioned LP unilaterally by local injections of ibotenic acid in three Macaca fuscata. We examined the effects of lesion on eye movements evoked by step (3 degrees )-ramp (5-15 degrees/s) moving target. To step-ramp moving target, the monkeys showed an initial slow eye movement and later a small catch-up saccade, which was followed by the post-saccadic pursuit nearly matching to the velocity of the ramp target motion. After LP lesioning, the velocity of post-saccadic pursuits in the ipsiversive and down-ward directions decreased by 20-40% in all three monkeys. These deficits lasted for at least 1 month, and some recovery was observed. In the amplitudes of catch-up saccades, no consistent changes were seen among the three monkeys after LP lesioning. These results suggest an involvement of LP in the primate smooth pursuit eye movement control.

Changes in expression of GABAA alpha4 subunit mRNA in the brain under anesthesia induced by volatile and intravenous anesthetics.

We investigated changes in levels of GABAA receptor alpha4 subunit mRNA in the mouse brain after administration of volatile or i.v. anesthetic, by performing quantitative RT-PCR. We also performed immunohistochemical assays for c-fos-like protein. During deep anesthesia (which was estimated by loss of righting reflex) after administration of propofol, levels of GABAA receptor alpha4 subunit mRNA in the hippocampus, striatum and diencephalons were significantly greater than those observed after administration of pentobarbital, midazolam or GOI (5.0% isoflurane and 70% nitrous oxide in oxygen). Under incomplete anesthesia, levels of GABAA receptor alpha4 subunit mRNA were significantly increased by midazolam in all brain regions, and were significantly increased by pentobarbital in the posterior cortex and striatum. Expression of GABAA receptor alpha4 subunit mRNA closely correlated with expression of c-fos-like protein. These results indicate that the GABAA receptor alpha4 subunit plays an important role in regulating the anesthetic stage of i.v. anesthetics.

Modulation of mThy28 nuclear protein expression during thymocyte development.

We have recently shown that down-regulation of mouse Thy28 (mThy28) protein expression appears to be accompanied by apoptotic processes. Thymocytes from mice contain moderate amounts of mThy28 protein and undergo proliferation, differentiation, or apoptosis during murine thymic maturation. As a first step to examine the potential role of the mThy28 protein in the thymocyte development, such as positive-negative selection, the expression of mThy28 protein in the thymocyte subsets was examined. Thymocytes are separated into four subpopulations by the expression levels of CD4 and CD8: CD4-CD8- (DN), CD4+CD8+ (DP), and CD4+CD8- or CD4-CD8+ (SP). Flow cytometry analysis using three-color staining demonstrated that the mThy28 expression in immature DP cells is lower than that in DN and SP cells. The down-regulation of the mThy28 expression in the DP stage was also detected by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). The immunostaining method also showed that mThy28 protein was expressed in the medulla containing mature thymocytes, but not the cortex having immature thymocytes. The mThy28 protein in the thymocytes was mainly localized in the nucleus, as recently demonstrated in lymphoma cells, indicating that the mThy28 protein resides in the nucleus, irrespective of the cyclic or resting stage of the cell cycle. Together, the observation that mThy28 expression is down-modulated during the DP stage suggests that mThy28 protein might play some role in the positive-negative selection step in thymic maturation.

Projections from the nucleus reticularis magnocellularis to the rat cervical cord using electrical stimulation and iontophoretic injection methods.

The aim of this study is to clarify the fiber distribution of the nucleus reticularis magnocellularis (NRMC) and adjacent areas in the rat spinal cord. Biotinylated dextran amine was injected iontophoretically through a glass capillary into the areas, in which a single cell responded to noxious electrical stimulation of the sciatic nerve and to a pinch of the thigh skin with multiple spikes. Labeled fibers descended bilaterally through the ventral funiculi of the medulla oblongata and then through the ventral and lateral funiculi of the cervical cord with an ipsilateral predominance, and terminated in the spinal gray (laminae I-X). A single fiber sometimes ran through several laminae while bifurcating many short branches with axon varicosities and terminal buttons in one transverse section, that is, through laminae V, VII and X, through laminae V, IIl-IV and I-II, and through laminae VII to I-II. The present study showed that the wide distribution of a single fiber and a mass of fibers descending from the NRMC and adjacent areas might modulate not only somatic sensory and motor functions but also autonomic functions in the spinal cord.